It's odd for the return value to be assigned to a variable so many
times, but never actually checked, but this has been the case since
the driver's inception in 2012.  If it hasn't caused any issues by
now, it's probably unlikely to.  Let's take it out, at least until
someone finds a reason to start using it.

Fixes the following W=1 kernel build warning:

 drivers/misc/lattice-ecp3-config.c: In function ‘firmware_load’:
 drivers/misc/lattice-ecp3-config.c:70:6: warning: variable ‘ret’ set but not used [-Wunused-but-set-variable]
 70 | int ret;
 | ^~~

Cc: Stefan Roese <sr@denx.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20200701085853.164358-13-lee.jones@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>